Process of producing calcium aluminate cement



Patented Oct. 30, 19 28.

UNITED STATES PATENT OFFICE.

ma ROCHE, or cAsrnLNAu-Ln-Lnz, ranxcn, ASSIGNOB. 'ro' ummm Bnmomz VOISIN, or cE'rrE-, rmcn .PBOCES8. OI PBODUGDIG CALCIUM'ALUMINATE CEMENT. I

I Drawing. Applied-loaned December 4, 1924, Serial Io. 754,008, and in France-Hay 6, 1924.

Mixtures of bauxite and calcareous materials employed for the v manufacture of aluminous cements, generally melt at a temperature very close to their point of softening or clinkering contrary to what is the case for Portland cement mixtures, for exam le. i

t follows that processes applicable to the manufacture of these last mentioned cements do not give good results in the case of' I aluminous cements, the substance being l1- able to. melt partially and then adhering to the walls of the kiln in such amanner as to impede the operation of burning This moreoveris the reason why the obtaining of aluminous cements has hitherto been confined to the employment of fusion processes, by means of the electric furnace and water jacket amongst others, which are expensive processes by. reason of the great Waste of heat involved.

The process according to the present invention is more economical. It consists in heating an alumino-calcareous mixture, suitably proportioned, to a low temperature duringa long period;a temperature of 900 to 1000 C. and a duration of 9 to 12 hours appear to give the best results, these examples eing in no Way limitative.

Under these conditions, partial melts are avoided and the mass uniformly undergoes a change in which the material comes together as an agglomerate but does not-enter that stage at which vitrification begins to occur. When in this condition it is softer than the usual'clinker, therefore more easily ground, besides which it is non-adhesive to the walls of the retort in which it is roasted. This binder by reason of its alumino-calcarcous composition resists sea water and selenitic waters. It possesses, moreover, by reason of the particular conditions of its burning, a certain number of excellent ualities, among which the most remarkab e is the rapidity of its hardening. It can be utilized immediately after grinding, without it bein necessary to allow it to remain stored 1n pits for a greater or less time. It

and sifted 67% of bauxite, this is much less fragile than ordinary aluminous cements and itssh'rinkage is almost Illl.

Emample.starting with a finely ground mixture of 33% fat lime and when perfectly uniformis watered and agglomerated into briquettes I of ordinary dimensions these briquettes after drying are burned at 900 C. in a continuous lime-kiln with natural draught, for

from 9 to 12 hours.

The frittedmaterial, obtained on withdra'wal from the kiln, after grinding and sifting. yields a cement which, even after only 24 hours, presents a very high resistance, its strength continiiing to increase with the lapse of time. Its duration of setting varies between 6 and 8 hours. This binder,

immersed in sulphated solutions or in pure at a temperature of about 900 to 1000 de-' grees centigrade. during about 9 to 12 hours.

3. A process for the manufacture of an aluminous cement, comprising, burning a mixture of bauxite anda lime at a temperacomprising, burninga and a calcareous ma-- ture of about 900 to 1000 degrees centigrade,

during a long period.

4. A process for the manufacture of an: aluminous cement, comprising, burning a. mixture of bauxite and a lime at a temperature of about 900 to 1000 degrees centigrade, during about 9 to 12 hours.

In testimony whereof I have signed my name to this specification.

' EMILE MARCEL: ROCHE. 

